Thanks @dmenezes for this info - it accords with my understanding of the change situation of the MC3000.
There appear to be three ‘versions’ of the MC3000: the ORIGINAL version (which had the problem with the sliders breaking off their posts and some other issues I can’t recall), the JUNE 2016 version which fixed all the problems, and then the POST 2016 version with the three bumps on the positive terminal and two fans.